| Structural highlights
6con is a 8 chain structure with sequence from "bacillus_tuberculosis"_(zopf_1883)_klein_1884 "bacillus tuberculosis" (zopf 1883) klein 1884. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
| | Gene: | gctA, CRX58_09925, ERS007663_04080, ERS007665_02371, ERS023446_02783, ERS027646_00148, ERS027654_03521, ERS027656_00696, ERS124361_01188, SAMEA2682864_02618, SAMEA2683035_00650 ("Bacillus tuberculosis" (Zopf 1883) Klein 1884), catJ, CRX58_09930, ERS007657_01926, ERS007661_02237, ERS007665_02370, ERS007670_03185, ERS007672_03945, ERS007679_04090, ERS007681_03977, ERS007688_03438, ERS007703_04697, ERS007722_01813, ERS007741_03174, ERS023446_02782, ERS024213_01521, ERS024276_02483, ERS027644_04603, ERS027646_00147, ERS027656_00695, ERS027659_03102, ERS027661_03605, ERS027666_03707, ERS124361_01187, SAMEA2682864_02619, SAMEA2683035_00651 ("Bacillus tuberculosis" (Zopf 1883) Klein 1884) |
| Resources: | FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT |
Publication Abstract from PubMed
Mycobacterium tuberculosis (Mtb) grows on host-derived cholesterol during infection. IpdAB, found in all steroid-degrading bacteria and a determinant of pathogenicity, has been implicated in the hydrolysis of the last steroid ring. Phylogenetic analyses revealed that IpdAB orthologs form a clade of CoA transferases (CoTs). In a coupled assay with a thiolase, IpdAB transformed the cholesterol catabolite (R)-2-(2-carboxyethyl)-3-methyl-6-oxocyclohex-1-ene-1-carboxyl-CoA (COCHEA-CoA) and CoASH to 4-methyl-5-oxo-octanedioyl-CoA (MOODA-CoA) and acetyl-CoA with high specificity (kcat/Km = 5.8 +/- 0.8 x 10(4) M(-1)s(-1)). The structure of MOODA-CoA was consistent with IpdAB hydrolyzing COCHEA-CoA to a beta-keto-thioester, a thiolase substrate. Contrary to characterized CoTs, IpdAB exhibited no activity toward small CoA thioesters. Further, IpdAB lacks the catalytic glutamate residue that is conserved in the beta-subunit of characterized CoTs and a glutamyl-CoA intermediate was not trapped during turnover. By contrast, Glu105(A), conserved in the alpha-subunit of IpdAB, was essential for catalysis. A crystal structure of the IpdAB.COCHEA-CoA complex, solved to 1.4 A, revealed that Glu105(A) is positioned to act as a catalytic base. Upon titration with COCHEA-CoA, the E105A(A) variant accumulated a yellow-colored species (lambdamax = 310 nm; Kd = 0.4 +/- 0.2 muM) typical of beta-keto enolates. In the presence of D2O, IpdAB catalyzed the deuteration of COCHEA-CoA adjacent to the hydroxylation site at rates consistent with kcat Based on these data and additional IpdAB variants, we propose a retro-Claisen condensation-like mechanism for the IpdAB-mediated hydrolysis of COCHEA-CoA. This study expands the range of known reactions catalyzed by the CoT superfamily and provides mechanistic insight into an important determinant of Mtb pathogenesis.
IpdAB, a virulence factor in Mycobacterium tuberculosis, is a cholesterol ring-cleaving hydrolase.,Crowe AM, Workman SD, Watanabe N, Worrall LJ, Strynadka NCJ, Eltis LD Proc Natl Acad Sci U S A. 2018 Mar 26. pii: 1717015115. doi:, 10.1073/pnas.1717015115. PMID:29581275[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Crowe AM, Workman SD, Watanabe N, Worrall LJ, Strynadka NCJ, Eltis LD. IpdAB, a virulence factor in Mycobacterium tuberculosis, is a cholesterol ring-cleaving hydrolase. Proc Natl Acad Sci U S A. 2018 Mar 26. pii: 1717015115. doi:, 10.1073/pnas.1717015115. PMID:29581275 doi:http://dx.doi.org/10.1073/pnas.1717015115
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